As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE "APP" BUTTON DOES NOT LIGHT WHEN DEPRESSED BUT THE FMA SHOWS THAT THE APPROACH/ILS IS ENGAGED. GROUNDED - YES. VERIFIED APP BUTTON INTERMITTENTLY WILL NOT ILLUMINATE WHEN DEPRESSED. FOUND THAT THE BUTTON WOULD SPRING OUT TOO FAR WHEN DEPRESSED, LOSING CONTACT INTERNALLY. REMOVED AND REPLACED DFCS MODE CONTROL PANEL IAW B737-800 AMM 22-11-34. PERFORMED ALL REQUIRED INSTALLATION TESTS IAW AMM 22-11-34. ALL TESTS PASS. PERFORMED ALL REQUIRED LLM MAINTENANCE TESTS IAW AMM 22-11-00. ALL REQUIRED TESTS PASS.